CARRIER MOVING MECHANISM

摘要

A carrier moving mechanism prevents backlash between a screw shaft (10) and a carrier (22) moved by this screw shaft. This carrier moving mechanism comprises a screw shaft and a carrier having secured thereon first and second nuts (26, 32) having teeth to be engaged with the thread (12) of the screw shaft. The teeth of the first nut are brought into contact with one side face of the lead of the screw shaft and the teeth of the second nut are brought into contact with the other side face of the thread (12) of the screw shaft (10) and the carrier (22) is moved through these first and second nuts (26, 32) by rotation of the screw shaft. The carrier moving mechanism also comprises a supporting carrier so that the supported nut can be rotated in the mechanism (38) which supports one of the nuts (32) on the rotational direction of the screw shaft (10) but the movement of the supported nut in the axial direction of the screw shaft (10) is restricted. Bias means (44) are provided for biassing the supported nut to rotate the supported nut in the direction eliminating the backlash and inhibiting means (50) are also provided for inhibiting the supported nut from rotating in the direction opposite to the direction of backlash-eliminating rotation, whereby the occurence of the blacklash due to wear of the teeth of the nuts and/or the thread of the screw shaft is prevented.